Virtual Image Display Optics for Reduced Double Images
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Solution Overview
Problem
Existing head-up display technologies require a large viewing distance to minimize double images, which limits their effectiveness regardless of the viewing distance to a virtual image.
Innovation Solution
A virtual image display device with a projection optical system that includes a projection mirror and an optical device of transmission type, where the light axis of the optical device intersects at an angle with the light path, and the display unit is positioned at the focal point of a composite optical system within the meridional plane, reducing astigmatism and double images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large viewing distance is used to reduce double images, then the amount of shift between double images decreases, but the effectiveness and visibility of the virtual image deteriorates
Solution Approach 1:
The patent changes the optical parameters of the projection system by introducing a projection mirror with specific curvature radius and positioning the display unit at the focal point of the composite optical system. This adjusts the light path geometry to reduce the shift between double images while maintaining virtual image visibility at appropriate viewing distances.
Solution Approach 2:
The projection mirror acts as an intermediary optical element between the display unit and the windshield. It mediates the light path by reflecting and focusing light to compensate for the double image effect caused by windshield interfaces, thereby reducing image shift without requiring extreme viewing distances.
2Device complexity
If conventional projection optics are used, then the system structure is simple, but double images and astigmatism occur reducing image quality
Solution Approach 1:
The optical system is segmented into distinct functional components: the display unit, the projection mirror with specific curvature, and the composite optical system with defined focal points. This segmentation allows each component to be optimized for its specific function while working together to eliminate double images and astigmatism.
Solution Approach 2:
The projection mirror is designed with a specific curvature radius to correct astigmatism and reduce double images. The curved surface of the mirror compensates for optical aberrations introduced by the windshield interfaces, improving image quality without significantly increasing system complexity.
3Measurement precision
If specialized windshield designs like wedge glass are used, then double images are reduced, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of modifying the physical windshield structure with specialized wedge glass designs, the patent creates an optical copy or compensation through the projection mirror system. The mirror system replicates the effect needed to reduce double images through optical path adjustment rather than physical windshield modification.
Solution Approach 2:
The patent replaces the mechanical approach of using specialized wedge glass windshield designs with an optical solution using a projection mirror. This substitution maintains the double image reduction effect while avoiding the manufacturing complexity and cost associated with specialized windshield fabrication.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the visibility of the virtual image by reducing double images and astigmatism, improving imaging performance without the need for specialized windshield designs like wedge glass.
Implementation Method 1
a projection mirror that projects the image display light toward the virtual image presentation plate
Implementation Method 2
an optical device of transmission type provided such that a light axis of the optical device intersects at an angle to a light path of the projection optical system
Implementation Method 3
the display unit is provided at a focal point of a composite optical system within a meridional plane... the focal point of the composite optical system within the meridional plane is a position of convergence of parallel beams
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
A virtual image display device 210 includes: a display unit 12 that generates an image display light L; and a projection optical system 214 that projects the image display light L toward the virtual image presentation plate. The projection optical system 214 includes a projection mirror 216 that projects the image display light toward the virtual image presentation plate 22 and an optical device of transmission type provided such that a light axis intersects at an angle to a light path of the projection optical system 214. The display unit 12 is provided at a focal point of a composite optical system 220 within a meridional plane, the composite optical system 220 being formed by the virtual image presentation plate 22 and the projection optical system 214, and the focal point of the composite optical system 220 within the meridional plane is a position of convergence of parallel beams assumed to be incident from the user E toward the virtual image presentation plate 22 along the meridional plane of the virtual image presentation plate 22.